1. Field of the Invention
The invention pertains to the field of plasma display panels. More particularly, the invention pertains to using glass structures, such as fiber, to construct a color plasma display panel.
2. Description of Related Art
Plasma display panels (PDP) have been around for about 30 years, however they have not seen widespread commercial use. The main reasons are the short lifetime, low efficiency, and cost of the color plasma displays. Most of the performance issues were solved with the invention of the three electrode surface discharge AC plasma display (G. W. Dick, xe2x80x9cThree-Electrode per PEL AC Plasma Display Panelxe2x80x9d, 1985 International Display Research Conf., pp. 45-50; U.S. Pat. Nos. 4,554,537, 4,728,864, 4,833,463, 5,086,297, 5,661,500, and 5,674,553). The new three electrode surface discharge structure, shown in FIG. 1, advances many technical attributes of the display, but its complex manufacturing process and detailed structure makes manufacturing complicated and costly.
Currently, plasma display structures are built up layer by layer on specialty glass substrates using many complex processing steps. FIG. 1 illustrates the basic structure of a surface discharge AC plasma display made using standard technology. The PDP can be broken down into two parts: top plate 10 and bottom plate 20. The top plate 10 has rows of paired electrodes referred to as the sustain electrodes 11a, 11b. The sustain electrodes are composed of wide transparent indium tin oxide (ITO) electrodes 12 and narrow Cr/Cu/Cr bus electrodes 13. These electrodes are formed using sputtering and multi-layer photolithography. The sustain electrodes 11 are covered with a thick (25 xcexcm) dielectric layer 14 so that they are not exposed to the plasma. Silk-screening a high dielectric paste over the surface of the top plate and consolidating it in a high temperature process step forms this dielectric layer 14. A magnesium oxide layer (MgO) 15 is deposited by electron-beam evaporation or sputtering over the dielectric layer to enhance secondary emission of electrons and improve display efficiency. The bottom plate 20 has columns of address electrodes 21 formed by silk-screening silver paste and firing the paste in a high temperature process step. Barrier ribs 22 are then formed between the address electrodes 21. These ribs 22, typically 50 xcexcm wide and 120 xcexcm high, are formed using either a greater than ten layer multiple silk-screening process, embossing a frit paste, or a sandblasting process. In the sandblasting method, barrier rib paste is blade coated on the glass substrate. A photoresist film laminated on the paste is patterned by photolithography. The rib structure is formed by sandblasting the rib paste between the exposed pattern, followed by removal of the photoresist layer and a high temperature consolidation of the barrier rib 22. Alternating red 23R, green 23G, and blue 23B phosphors are silk-screened into the channels between the barrier ribs to provide color for the display. After silk-screening the phosphors 23, the bottom plate is sandblasted to remove excess phosphor in the channels. The top and bottom plates are frit sealed together and the panel is evacuated and backfilled with a gas mixture containing xenon.
The basic operation of the display requires a plasma discharge where the ionized xenon generates ultraviolet (UV) radiation. This UV light is absorbed by the phosphor and emitted as visible light. To address a pixel in the display, an AC voltage is applied across the sustain electrodes 11, which is large enough to sustain a plasma, but not large enough to ignite one. A plasma is a lot like a transistor, as the voltage is increased nothing happens until a specific voltage is reached where it turns on. Then an additional short voltage pulse is applied to the address electrode 21, which adds to the sustain voltage and ignites the plasma by adding to the total local electric field, thereby breaking down the gas into a plasma. Once the plasma is formed, electrons are pulled out of the plasma and deposited on the MgO layer 15. These electrons are used to ignite the plasma in the next phase of the AC sustain electrodes. To turn the pixel off, an opposite voltage must be applied to the address electrode 21 to drain the electrons from the MgO layer 15, thereby leaving no priming charge to ignite the plasma in the next AC voltage cycle on the sustain electrodes. Using these priming electrons, each pixel can be systematically turned on or off. To achieve gray levels in a plasma display, each video frame is divided into 8 bits (256 levels) and, depending on the specific gray level, the pixels are turned on during these times.
A number of methods have been proposed to create the structure in a plasma display, such as thin and thick film processing, photolithography, silk screening, sand blasting, and embossing. However, none of the structure forming techniques provides as many advantages as using fibers. Small hollow tubes were first used to create structure in a panel by W. Mayer, xe2x80x9cTubular AC Plasma Panels,xe2x80x9d 1972 IEEE Conf. Display Devices, Conf. Rec., New York, pp. 15-18, and R. Storm, xe2x80x9c32-Inch Graphic Plasma Display Module,xe2x80x9d 1974 SID Int. Symposium, San Diego, pp. 122-123, and included in U.S. Pat. Nos. 3,964,050 and 4,027,188. These early applications were focused on using an array of gas filled hollow tubes to produce the rib structure in a plasma display panel. In addition, this work focused on adding the electrode structure to the glass plates that sandwiched the gas filled hollow tubes.
Since this early investigation, no further work was published on further developing a fiber or tube technology until C. Moore and R. Schaeffler, xe2x80x9cFiber Plasma Displayxe2x80x9d, SID ""97 Digest, pp. 1055-1058. This work integrated the wire electrode(s) into glass fibers to produce the structure in a display, as shown in FIG. 2. U.S. Pat. No. 5,984,747, issued Nov. 16, 1999, entitled xe2x80x9cGLASS STRUCTURES FOR INFORMATION DISPLAYSxe2x80x9d, was granted covering this technology. Another fiber-based plasma display patent application, Ser. No. 09/299,370, filed on Apr. 26, 1999, entitled xe2x80x9cFIBER-BASED PLASMA DISPLAYSxe2x80x9d, covers many different additions to the structure in the fiber-based plasma display and is incorporated herein by reference. The manufacturing of the plasma display covered under U.S. Pat. No. 6,247,987, issued Jun. 19, 2001, entitled xe2x80x9cPROCESS FOR MAKING ARRAY OF FIBERS USED IN FIBER-BASED
DISPLAYSxe2x80x9d, and patent application, Ser. No. 09/299,371, filed Apr. 26, 1999, entitled xe2x80x9cFRIT-SEALING PROCESS USED IN MAKING DISPLAYSxe2x80x9d, allow for the manufacturing of any multiple strand arrayed plasma display and are incorporated herein by reference.
There are several advantages to creating plasma displays using arrays of fibers. The largest advantage is a reduction in the manufacturing costs of the panel of over a factor of two with a five times less capital cost requirement. These economical advantages result from manufacturing process with no multi-level alignment process steps, no need for large area vacuum deposition equipment, about xc2xd the process steps (potentially leading to higher yields), simpler process steps (hot glass extrusion, fiber draw, and phosphor spraying compared to photolithography, precision silk screening, and vacuum deposition processes) and the ability to create many different size displays using the same manufacturing equipment. Although using fibers to create the structure in a display has drastically simplified the manufacturing of the panel leading to a large reduction in manufacturing cost, there have been no advancements to the performance of the display. Plasma displays still suffer from low luminous efficiencies and poor color purity, mainly due to a lack of blue phosphor. NEC Corporation has been fabricating plasma displays using a color filter contained within the top plate and aligning the color filter with the corresponding phosphor colors in the bottom plate, as described in U.S. Pat. No. 6,072,276, issued Jun. 6, 2000, entitled xe2x80x9cCOLOR PLASMA DISPLAY PANEL AND METHOD OF MANUFACTURING THE SAMExe2x80x9d. The addition of a color filter has created a display with a much higher color purity and higher bright room contrast. Adding color filters to plasma displays was first patented by Pioneer Electronic Corporation in U.S. Pat. No. 5,838,105, issued Nov. 17, 1998, entitled xe2x80x9cPLASMA DISPLAY PANEL INCLUDING COLOR FILTERSxe2x80x9d.
This patent describes a new fiber-based plasma display that economically incorporates a color filter and whose structure is designed to yield the maximum luminous efficiency.
The invention includes an array of complex shaped top fibers which each contain an address electrode, barrier ribs to form a plasma channel and a phosphor coating on the plasma channel to create the structure in a plasma display panel. The top fiber array is disposed on the plate facing the viewer and the light generated by the phosphors must penetrate through the top fibers to the viewer. The top fibers can be composed of a colored material associated with the color phosphor layer to add color purity and contrast to the plasma panel. The sustain electrodes are placed on the plate facing away from the viewer and can be included in an array of fibers containing wire sustain electrodes. Since the light is transmitted through the top fiber array the sustain electrode surface does not have to be transmissive. Therefore, the sustain electrodes can be composed of a reflective metal and cover the majority of the surface of the bottom plate. Covering a large percentage of the bottom plate with sustain electrodes causes the maximum spreading of the electric field and generates the highest plasma efficiency. The sustain electrode bottom plate or array can also be reflective to reflect both the UV generated by the plasma back toward the phosphor layer and the visible light generated by the phosphor layer back toward the viewer.